Aug. 15, 2007 If efforts now under way by a team of University of Wisconsin-Madison engineers pan out, the age of the nanomechanical computer may be at hand.
Instead of relying on solid-state transistors and other electronic components to compute ones and zeroes, such a machine would depend purely on moving parts - gates and pillars and levers and pistons - to create switches, logic gates and memory units, the building blocks of digital computers.
"The aim is to have a new type of device for computing applications," says Robert Blick, a UW-Madison professor of electrical and computer engineering and senior author of a paper in the July 24 New Journal of Physics that outlines a plan for making a computer based on microscopic moving parts.
Conventional devices use electrons that travel in circuits to perform the calculations that drive the functions of computer chips. A nanomechanical computer would also depend on electrons, but instead of the solid state electronic components used in conventional computers to channel them into working circuits, the nanomechanical device would rely on the push and pull of millions of microscopic parts to control the flow of electrons.
Inspiration for the Wisconsin effort resides in the purely mechanical computers of the past. The most famous is the "difference engine" produced by 19th century English mathematician Charles Babbage. Hand-held mechanical calculators, Blick notes, were developed in the 1950s and were sold as recently as the early 1970s.
Computer chips based on nanomechanical parts are not likely to compete with conventional electronic devices, Blick says, but they would have key advantages that could lead to hybrid chips or specialized roles for all-mechanical nanodevices.
For example, nanomechanical chips promise to be more rugged and durable than conventional silicon chips, making them potentially useful for extreme environments such as space, car engines, battlefields and children's toys. What's more, they would require less power to operate and could perform at much higher temperatures - up to 500 degrees Celsius - obviating the need for the energy-eating cooling systems required for electronic, silicon-based computers.
It's estimated that between 15 and 20 percent of total energy use in the United States is devoted to operating and cooling computers. "That's one of our motivations. That's why we have this dream to attack the problem at the root," Blick says.
More energy-efficient chips would also have potential for portable computers, as battery power tends to be the limiting factor for laptops.
Blick's group has already made a working silicon model of a mechanical transistor, the basic switch at the heart of all computers, and is now in the process of trying to align several elements into a working circuit.
"We've tested these single devices and we've shown that a single element works," says Blick. "The next step is to demonstrate memory. We're starting with the basics of information engineering."
The components of a nanomechanical computer, according to Blick, would likely be made of materials other than silicon. Ultra-hard diamond film is one possible material, as it can be chemically treated and is amenable to the methods used to mass-produce integrated circuits.
An important consideration, Blick explains, is developing a system that can achieve industrial-scale production and uses existing industrial lithographic techniques.
"We have some idea of how to mass-fabricate (these devices) in the clean room," Blick says. "We think it might be four years to having a product."
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